1. Field of the Invention
The present invention relates to a semiconductor device with a silicide layer and a manufacturing method thereof, and more particularly, to a semiconductor device with a silicide layer having excellent thermal stability, and a manufacturing method thereof.
2. Discussion of Related Art
In manufacturing a semiconductor device such as a thin film transistor, particularly, containing silicon, an electrical contact is made between a gate and a drain-source through a metal process. In recent years, as the integration of the semiconductor device increases, a contact region between the gate and the source-drain considerably becomes small (about 100 nm or less), thereby increasing contact and surface resistances and increasing resistor-capacitor (RC) delay. This reduces an operation speed of the silicon semiconductor device.
In order to solve such a problem, a method is widely used which forms a silicide layer (stable metal compound resulting from reaction of silicon and metal) in the contact region between the gate and the source-drain to reduce the surface resistance and the contact resistance. As the silicide layer, titanium silicide (TiSi2) and cobalt silicide (CoSi2) are most widely used to manufacture the stable silicon semiconductor device. The TiSi2 and CoSi2 have a low specific resistance suitable for all device operations.
However, according to “J. Electrochem. Soc. 144, P 2437” announced by D. K. Sohn et al. in 1997, in the case of the TiSi2, as a line width narrows, it is difficult to phase transform from C-49 TiSi2 having a high specific resistance to C-54 TiSi2 having a low specific resistance, and a bridge phenomenon causing an electrical short circuit between the source-drain and the gate may appear. CoSi2 has more merits than the TiSi2, but has a drawback in that, according to “Mater. Sci. Eng. R. 16, p 43” announced by E. G. Colgan et al. in 1996 and “Materials Chemistry and Physis 52, P 99” announced by J. P. Gambino et al. in 1998, cobalt (Co) and silicon (Si) have very active reactivity, causing spark in cobalt silicide (CoSix) and, since Si much more than other silicides is needed to generate a predetermined amount of the CoSi2, it is very difficult to form the CoSi2 on a shallow junction at a low junction leakage current level.
In recent years, in order to overcome the above defects occurring from the TiSi2 and the CoSi2, nickel mono-silicide (NiSi) is contrived as a new silicide material having a good characteristic, and is used to manufacture a high-performance silicon semiconductor device. However, in the case where the NiSi is applied to the silicon semiconductor device, there is a drawback in that, as an annealing temperature increases, the sheet resistance abruptly increases, thereby deteriorating thermal stability and causing a leakage current. According to “Tech. Dig. Int. Electro Device Meet, p 453” announced by T. Ohguro et al, these drawbacks are known to result from oxidation of a NiSi thin layer caused by oxygen pollution. A method widely used to solve the drawback of the NiSi is to use a TiN capping layer.
In this method, as disclosed in Japan Patent Laid-Open Publication No. 1995-038104 and U.S Patent Laid-Open Publication No. 2004-97060, the TiN capping layer is deposited on a Ni layer as a diffusion prevention layer against oxygen, thereby forming a NiSi layer. However, in the case where the TiN capping layer is used, oxygen pollution can be effectively prevented, but there is a disadvantage in that, due to great interface roughness between the NiSi thin layer and the silicon substrate, thermal stability for subsequent annealing is deteriorated. As another method of preventing the oxygen pollution at the time of forming the NiSi thin layer, as disclosed in “IEEE Electron Device Letters Vol. 29, p 572” announced by Tuo-Hung Hou et al. in 1999, there is a method using a Ti layer as the diffusion prevention layer. This method has an advantage of providing high thermal stability together with prevention of the oxygen pollution but, has a drawback in that the oxygen pollution cannot be effectively prevented as much as the TiN capping layer and, in addition, since the Ti layer easily reacts with peripheral adjacent material due to its great reactivity, an exact and uniform process cannot be performed.